1. Field of the Invention
The invention relates to a method of treating and processing alkaloid-, oil- and protein-containing lupine seeds for the production of lupine seed products by means of selective fractioning.
2. Prior Art
Proteins are considered to be raw materials for the food and food-processing industries and are used for many applications in industrial chemistry, for instance for the production of adhesives, emulsions for photographic layers, as well as cosmetics; just to enumerate some of them.
As proteins are an essential component in animals and plants, they are renewable native raw materials which can be produced on an industrial scale, e.g. from milk, soy beans and wheat. Lupine seeds, which resemble soy beans in their composition in view of protein level, crude fiber percentage and oil percentage, are of particular importance for protein production. Lupine cultivation and the processing of lupine seeds for producing the desired protein products is therefore particularly interesting because lupines can be cultivated in regions which are not appropriate for soy beans, such as Western Europe or Australia.
A direct use of lupine products, specifically for food applications, is restricted on account of naturally occurring bitter principles, caused by so-called alkaloids, and in case of the so-called bitter lupines, which are expedient from a cultivation point of view, are entirely precluded. When lupine seeds are processed, it is therefore necessary to eliminate the alkaloids in order to obtain products for use as food. At the same time, the extracted alkaloids can be selectively used as active components in agriculture and pharmacy, which renders the complete utilization of lupines or bitter lupines, respectively, extremely interesting also from an economic viewpoint.
From the German Patent DE 537 265, which was published in 1931, a method is apparent for the useful utilization of lupines with disembitterment removes bitterness by stepwise extraction with aqueous solutions. Disembitterment is performed by staged extraction in a wet condition from lupine chips, with the addition of an acid and subsequent dissolution of the salts formed in the acid bath.
Moreover, WO 83/00419 discloses a method of and a device for elimination of the bitter principles from bitter-lupine seeds, according to which the lupines in a most finely ground form are subjected to a rinsing with lupine extract solutions of different concentrations, with application of the counter-current principle, with water being used as solvent.
An improved method of disembitterment of lupine seeds is disclosed in WO 97/12524, which provides for an initial shredding of the lupine seeds to form grits-like granules having diameters between 200 and 600 xcexcm, and then a thermal processing of the plant seeds, which achieves a selective deactivation of enzymes present in the plant seeds. The thermal influence is produced directly by means of a blanching technique, i.e. the direct introduction of hot steam into the crushed seeds. Following the blanching operation the plant seeds are subjected to a disembitterment process comprising two steps, whereof the first extraction step results in the separation of the alkaloids and other non-nutritive substances. To this end the plant seeds are mixed with fresh drinking wafer as solvent in an acidic medium using counter-current extraction. The mixing operation can preferably be performed in goveral stages until an extract enriched with non-nutritive substances and an extractable refined product is produced which is rich in proteins and roughage. The refined product produced from the first extraction step is added, in a second step, with water as solvent in an alkaline medium. A result of the extraction in the second step is both a refined product enriched with roughage and a protein milk enriched with proteins.
All the aforedescribed disembitterment processes are based on a common objective, i.e. firstly the production of proteins in the purest form possible, and secondly obtaining roughage disembittered as completely as possible for the food or food processing industries.
The aforedescribed methods entail, however, also various inherent disadvantages: on the one hand, plant seeds, and specifically lupine seeds, have an oil percentage of roughly 10 to 15%, which contains not only pure oil such as triglycerin but also lipophilic secondary constituents such as carotinoids, lecithins or lipophilic alkaloids. The latter constituents, in particular, cannot be sufficiently extracted by the known disembitterment processes so that the disembittered final products unavoidably contain lipophilic alkaloid residual components.
Even though the known method according to WO 97/12524 provides for a deactivation of the enzymes present in the plant seeds, which precedes the disembitterment process, the occurrence of an enzymatic oxidation of present unsaturated fatty acids during storage of the disembittered products can be precluded, which fatty acids would, for instance, give rise to a rancid flavor, which is undesirable for use in the food sector. However, the deactivation is performed by way of blanching, which means that the plant seeds are subjected to hot steam, which, even though the enzymes are deactivated, is unavoidably detrimental thereto and also to accumulation proteins such that they lose their native form and properties.
Eventually, the shaping of the crushed lupine seeds contributes as well to the success of the disembitterment process. The grits granule shape proposed in WO 97/12524, for instance, is inexpedient insofar as it encompasses a comparatively large volume from which the individual constituents to be extracted must be eliminated, which means that the substances to be extracted can leave the grit-shaped lupine seed components to be disembittered more difficult the greater the distance is from the interior of the volume to the outside of each grits granule. On the other hand, it is proposed in WO 83/00419 to grind the lupine seeds to be disembittered to form ultra-fine meal having a granularity between 1 xcexcm and 50 xcexcm, which, however, gives rise to problems in terms of process engineering when the liquid and solid phases are separated, on account of the fine grinding of the lupine seeds for producing a meal, even though the individual extraction paths inside a xe2x80x9cdust grainxe2x80x9d are maintained very small. This requires complex filtering steps, which are expensive in terms of process engineering and which involve a substantial cost and time factor in an industrial application.
The present invention is a method of treating and processing alkaloid, oil and protein containing lupine seeds for the production of lupine seed products by means of selective fractioning in such a way that the proteins in purest form, as well as roughage, are freed of bitter principles as completely as possible, while the steps of operation to be realized in succession should involve the lowest possible industrial expenditure. On the one hand, particular attention is paid to the fact that the proteins to be treated must remain unchanged in their native form whereas enzymes contained in the lupine seeds are deactivated, and lipophilic alkaloids in particular are extracted most completely in the most gentle manner possible. The process comprises the simplest, mutually matched process steps for a substantial improvement of the degree of disembitterment of lupine seeds so far reached, or reducing the engineering expenditure substantially with the same result of disembitterment.
In accordance with the present invention, in the method of treating and processing alkaloid, oil and protein containing lupine seeds for the production of lupine seed products which are both rich, the go-called bitter lupines, or poor in bitter principles, by means of selective fractioning, the following steps of method are performed:
Initially, the lupine seeds are husked and the husks are separated. It is particularly advantageous for the further steps of the method to screen the lupine seeds by shape and size either before or during husking. For this operation screens of an appropriate mesh size may be used for realizing the screening operation. The husking operation is performed by a cold process in which the lupine seeds are halved and subsequently freed of their husks. Then the fleshy nuclei of the seeds are crushed or shaped, respectively, to form platelet-like flakes which are exposed in this form to an indirect introduction of heat while water is largely excluded. The flakes are preferably formed by means of flaking rollers which have a temperature below the denaturation temperature of the lupine proteins, i.e. less then 40xc2x0 C.
Due to a gentle indirect introduction of heat, the enzymes contained in the lupine seeds are deactivated while the proteins largely retain their original shape and their functional properties because they do not come into direct contact with water, which would cause damage to the natural properties of the proteins.
In accordance with the present invention, the flakes are now subjected to a selective deoiling process in which a solvent is used, preferably hexane which allows for extraction of the lipids contained in the platelet-shaped flakes. In particular, the extracted lipids relate also to all lipophilic alkaloids contained in the lupine seeds, which can be isolated by de-oiling so that merely lipophobic alkaloids are still present as a result of bitter principles in the hexane-soaked platelet-shaped flakes, which must then be extracted in a subsequent disembitterment process. Then benzenes are preferably gently removed from the hexane-soaked meal, for instance by means of supercritical hexane.
What has turned out to be particularly expedient is an indirect thermal treatment of the de-oiled flakes, which may be performed, for instance, by means of a thermal pan.
For disembitterment the benzene-freed, lipid-reduced, platelet-shaped flakes are subjected to an aqueous fractioning process congisting substantially of two process steps:
Initially, the de-oiled flakes are introduced into an aqueous acidic medium where all those substances are dissolved which are contained in the flakes and can be dissolved in the acidic range. As a results an aqueous acid extract is obtained which contains particularly the alkaloids as well as a disembittered refined product, insoluble in the acidic range, which consists substantially of flake material.
The flakes so extracted, which are also referred to as meal, can then be subjected to a further subsequent extraction which aims at the production of isolated proteins or concentrations, respectively. In the subsequent extraction, too, aqueous systems are involved which can be joined in several successive stages. The solid and liquid phases can be separated by means of decantation which furnishes the protein extract as well as protein-depleted extracts or their compartments as product, with the protein traction remaining in the remaining flake substance being capable of being controlled by means of specific process conditions such as the pH level, extraction periods and temperatures.
When the refined product which is insoluble in acids is introduced into an aqueous alkaline medium in which all those substances are dissolved which dissolve in the alkaline range, i.e. at pH levels higher than 7.5, an alkaloid-reduced refined product is obtained as a final result, which is available immediately after the second process step, which refined product is free of both any lipophilic alkaloids and alkaloids soluble in the acidic range.